This invention relates to laser tools used in construction measurement and the use of laser beams to indicate reference lines and planes. In particular, the invention relates to locating lines at 90 degrees (or other angles) to each other in the horizontal planes as are commonly used in the construction industry. Laser instruments of this type project a beam or beams of laser light which indicate points along a line. The line may be an element of a horizontal plane. The invention consists of a self-leveling laser with a wide self-leveling range and a remote-controlled turntable which is easily detachable from the laser.
In the simplest case of the prior art, a laser projector is mounted to a carpenter's level and projects a laser beam parallel to the axis of the level. The spot produced by the beam striking a surface along the projected line indicates a point on the level reference line. This basic laser tool is described in Genho U.S. Pat. No. 3,897,637. In this case, the carpenter's level must be adjusted to level using the level vials on the instrument. In Rando U.S. Pat. Nos. 4,852,265, 4,912,851, Hersey U.S. Pat. No. 5,144,487 and Rando U.S. Pat. No. 5,075,977, as well as in copending Rando application Ser. No. 248,517 (filed May 24, 1994) a self-leveling laser instrument is described which projects a level laser beam despite the tilt of the housing. A reference plane can be generated by rotating the above self-leveling laser instrument about a point on a substantially horizontal surface. Since the height of the instrument has not changed substantially during the rotation, every projected line is an element in the level plane.
Today it is most common to generate the laser reference plane by projecting the laser beam into a rotating pentaprism. This technique is described in Studebaker U.S. Pat. No. 3,588,249, Aldrink U.S. Pat. No. 3,936,197, Rando U.S. Pat. Nos. 4,062,634 and 4,221,483, Borkovitz U.S. Pat. No. 4,993,161 and others. In all cases, the housing is fixed and a beam is rotated to generate a plane. Normally these instruments are mounted on a tripod and require setup by the operator. The tripods are generally heavy and clumsy to carry and set up. Most of the self-leveling laser instruments require an adjustment base under the laser or on the instrument to adjust the base of the instrument to be within the self-leveling range. Most of these instruments have a self-leveling range of only 15 minutes of arc requiring some time to set up. This set-up time is costly for the operator. Instruments with a self-leveling range of several degrees do not require adjustments for leveling and thus are more productive to use.
Generally speaking, a rotating beam is too weak to see and a sensitive detector is needed. To locate the beam the detector is manually raised and lowered in the beam to locate center. A visual display on the detector or an audio tone indicates the beam position to the user. The goal of the instrument described above and the present invention is to mark points at the same elevation or along a given line. When the beam is not rotating, the center of the spot may be marked with a pencil. When a detector is used, a reference notch on the detector guides the pencil mark.
It is sometimes common to point a stationary laser beam with the same motor which is normally used to rotate the beam continuously. In this way, the operator can mark desired locations within the job site without using an expensive detector. When the spot is visible on the wall, it is quickly and easily marked with a pencil. The disadvantage of this system is that the operator must move the beam to a new location for each point. This means he must walk back and forth between the laser and the point to be marked, which is very time consuming.
In the prior art shown in FIG. 1, a level plane may be established by positioning a self-leveling laser instrument over a point and rotating the instrument as needed to mark points in the plane. In this case, the operator must walk back and forth between the laser instrument and to make each mark, which as noted above is time consuming. The laser instrument shown in FIG. 1 has two beams at 90 degrees to each other which can be used to represent a building corner.
In the tripod mounted laser instrument shown in FIG. 2, the rotating head may be used to point the beam at the locations desired. Such pointing can be done manually or with a remote control device (not shown). In the tripod mounted instrument the laser beam was rotated internally in the instrument, via a pentaprism, and the instrument was self-leveling only within a very narrow range. The instrument lacked the versatility of a hand-carryable, self-leveling instrument, useful separately from a remotely controlled turntable as in the present invention described below.